The provisions of this article do not apply to the Army, Navy, or Air Force of the United States, the National Guard, and organizations authorized by law to purchase or receive machine guns, military firearms, or sawed-off shotguns or sawed-off rifles, from the United States or from this State and the members of these organizations. Any peace officer of the State or of any county or other political subdivision thereof, state constable, member of the highway patrol, railway policeman or warden, superintendent, head keeper or deputy of any state prison, penitentiary, workhouse, county jail, city jail, or other institution for the detention of persons convicted or accused of crime or held as witnesses in criminal cases or person on duty in the postal service of the United States or any common carrier while transporting direct to any police department, military, or naval organization or person authorized by law to possess or use a machine gun, or sawed-off shotgun, or sawed-off rifle, may possess machine guns, or sawed-off shotguns, or sawed-off rifles, when required in the performance of their duties, nor shall the provisions hereof be construed to apply to machine guns, or sawed-off shotguns, or sawed-off rifles kept for display as relics and which are rendered harmless and not usable.

The provisions of this article do not apply to any manufacturer of machine guns or military firearms licensed pursuant to the provisions of 18 U. S. C. Section 921 et seq., nor to any common or contract carrier transporting or shipping any machine gun or military firearm to or from the manufacturer if the transportation or shipment is not prohibited by federal law, nor to persons licensed pursuant to Section 23-31-370.